An estimated 25-40 million people in Bangladesh have been exposed to a high level of arsenic from the ground water which is the source of drinking water for 97% of the country's population. The most common health condition produced by arsenic among the Bangladesh population is skin lesions ranging from melanosis and keratosis of the skin to squamous and basal cell carcinomas of the skin. The goal of this pilot study is to determine, for the first time, the epidemiological and molecular characteristics of the arsenic-induced skin lesions and their etiologic co-factors among the Bangladesh population. The specific aims of the pilot study are to: 1. Collect interview data, water, and biological samples from subjects (n=50) who are affected with the arsenic-induced skin lesions in 6 designated villages in Bangladesh and a sample of control subjects (n=50) from the same areas who are not affected with the skin lesions. 2. Examine the epidemiological and clinical characteristics including the age of onset, pattern of skin involvement, latency period and duration of symptoms, dose response relationship with arsenic exposure, clinical course, and comorbidities of the arsenic-induced skin lesions among the study subjects. 3. Examine the molecular characteristics including the histopathological features and mutations in the tumor suppressor genes p53 and PTCH and expression of the keratinocyte-derived growth factor TGFa in arsenic- induced skin lesions. 4. Determine the genetic (including polymorphisms in the DNA-repair gene XPD and carcinogen-metabolism gene GSTP1) and other host factors (including age, sex, diet, nutritional status, reproductive factors, and smoking) that are related to the onset, progression and molecular alterations of the arsenic-induced skin lesions.